The synthesis of ribosomes during Xenopus oogenesis and early development is an excellent example of a developmental process amenable to study at the molecular level. cDNA and genomic clones for representative cytoplasmic and mitochondrial ribosomal protein genes will be isolated and used to determine the basic parameters of ribosomal protein gene structure and expression throughout Xenopus development. Anucleolate embryos will be used to probe the mechanisms by which cytoplasmic and mitochondrial ribosomal protein genes are regulated independently. The following experiments will establish a correlation between specific DNA sequences and specific events controlling ribosomal protein gene expression. First, the complete DNA sequence of cloned ribosomal protein genes will be determined. Second, the regions of each gene which code for ribosomal protein mRNA and the locations of any intervening sequences will be resolved. This will enable a detailed quantitative and qualitative definition of the events controlling mRNA production during development. Third, the production of authentic ribosomal protein gene products upon microinjection of cloned genes into Xenopus oocytes will be assessed. This system will be assayed in detail to determine which mechanisms of ribosomal protein gene expression function faithfully and efficiently. Finally, specific DNA sequences of ribosomal protein genes will be altered by in vitro mutagenesis and assayed for expression of MRNA in the oocyte-injection system. These studies will provide a basis for understanding the mechanisms controlling coordinate expression of a large number of genes during normal development. Such knowledge is essential in elucidating the abberant control events responsible for developmental abnormalities and neoplasia.